1. Field of the Invention
This invention relates to the field of wireless communication systems. More specifically, the present invention relates to a power management system for mobile stations.
2. Description of the Related Art
The use of wireless communication systems is growing with users now numbering well into the millions. However, one inconvenience associated with routine use of a mobile unit is the constant need to recharge and replace depleted batteries. Even users who make and receive very few telephone calls wherein their mobile units operate mostly in a standby mode (awaiting calls) experience the annoying and frequent problem of depleted battery power.
A large portion of battery power consumed in common standby modes is attributable to call detection processing. For example, in the Global System for Mobile Communications (GSM) wireless communication networks, about once every second, a mobile unit receives and decodes a paging message. The mobile unit processes the paging message to detect in-coming calls. Only rarely does the detection attempt result in discovery of an in-coming call. Unfortunately, a great deal of battery power is consumed in this call detection process.
Base stations transmit paging messages to mobile units based upon the number of mobile units in the base station's area of service. Frequently paging the mobile units reduces the time required to detect an in-coming call. Thus, one reason to frequently page a mobile unit is to minimize the delay between routing a call from the base station to the mobile unit.
As with any transmitted signal, the quality of the signal received by the mobile unit varies based upon a number of factors, including atmospheric conditions, location of the mobile unit, or interference by terrain or buildings. If a paging message received by the mobile unit has degraded, the mobile unit may be unable to decode and process the message. For example, atmospheric conditions may degrade the signal prior to reaching the mobile unit, or the mobile unit may be at the outer transmission boundary of the base station.
Base stations therefore retransmit each paging message multiple times to ensure the mobile station eventually receives a good signal. The number of times the base station retransmits the paging message varies depending upon the service provider. Thus, frequently retransmitting paging messages reduces the delay caused by transmission errors.
In conventional systems, the base station establishes the frequency the paging messages are sent to the mobile units. The frequency which a base station sends paging messages to a mobile unit is related in part to the number of mobile units and in part to the number of times paging messages are retransmitted. For example, if a base station is serving only a few mobile units, the base station may be able to send a paging message to each mobile unit more often. However, if the base station is serving a large number of mobile units, it may take more time to send paging messages to each mobile unit. Likewise, if a base station retransmits a paging message multiple times, it may take more time to send paging messages to each mobile unit.
Improvements in battery technology, while helpful, have done little to avoid the seemingly ever-present need to recharge and replace mobile unit batteries. What is needed is a system to conserve battery power by minimizing the power consumed when processing paging messages.